Alarm circuit



Patented Nov. 19, 1935 UNITED STATES ALARM CIRCUIT Roger W. McBrien, Alton, and Norval F. Wilson,

East Alton, 111.; said Wilson assignor to said McBrien Application March 11, 1932, Serial No. 598,192

2 Claims. (Cl. 177356) Our invention has relation to improvements in electric alarm circuits and it consists in the novel features of construction more fully set forth in the specification and pointed out in the claims.

'The present invention is an improvement over that shown in our pending application, Serial No. 583,434, filed December 28, 1931, and, like that, is particularly directed to an alarm circuit which 1 0 may be connected to various power circuits in buildings and residences primarily for sounding, or otherwise giving an alarm in case of fire, and secondarily for permanently opening a circuit that has been shorted.

The object of the present invention is to simplify the circuit described in the above mentioned .application, which we accomplish by providing an asymmetric cell across the power circuit and a second asymmetric cell opposed thereto in the safety circuit that comes into activity to open the power circuit in case of a permanent short therein. The manner in which this is accomplished, together with the advantages inherent in our improved device, will be better apparent from a detailed description of the invention in connection with the accompanying drawing, in which:

Fig. 1 is a diagrammatic view of our improved alarm circuit applied to two power circuits connected in parallel; Fig. 2 is a wiring diagram of a modified form of the control circuits that cause the actuation of the safety circuits for the respective power circuits in the building that is to be protected by the device; and Fig. 3 shows a modification of the respective safety circuits, in

which the relays are replaced by thermostatically operating switches.

Referring to the drawing, the power circuits comprise conductors I, 2 and. I, 2, conductors l, I being directely connected to line wire L, and

conductors 2, 2' being connected to fuses 6, 6' by conductors 3, 3. Conductors 4, 4 connect the fuses 6, 6' to line wire L'. The ends of fuses 6, 6' connected to conductors 3, 3 are also connected by conductors 8, 8 to the pivots 5, 5',

on which are mounted similar double contact switch levers 1, I. Spring contacts 9, 9' are mounted adjacent to the ends of switch levers I, I and said levers are normally held out of contact with said contacts by triggers l0, I0,

which comprise armatures within coils I I, II. It will be observed that in the drawing the switch lever 1 is shown in its normal position while the switch lever I is shown after it has been released to engage contact 9. Correspond- 1 ing ends of coils H, II are connected t -v ling wire L by conductors I 2, I2 respectively, while the opposite corresponding ends of said coils are connected to arinatures I0, I0 respectively.

The switch levers I, 'I' and associated parts just described constitute relays for connecting their 5 respective power circuits to the alarm circuit should a fire or a short circuit occur in one of the power circuits, as will be more apparent hereinafter.

Our alarm circuit is primarily intended to give 10 an alarm in case of a fire, consequently, thermostatic switches of any common type are distributed throughout the building that is protected by our invention. Each thermostatic switch I3 is connected in series with an asymmetric cell 15 it connected across the respective power circuits. Therefore, when any switch I3 is closed by the heat of a fire in the building, current will flow through the cell I5 and switch l3 in the circuit containing the closed switch. 20

The foregoing description shows that fuses 6 r and 6' and coils II and II are in parallel-series connection with the power circuit and that when these circuits are operating under load, current will flow through the fuses 6 and 6'. However, 25 when either of the thermostatic switches I3 is closed there will be a heavy current flow through either fuse '5 or 6', which will be blown and cause the current to flow through either coil I I or 30 H.

Assuming that thermostatic switch l3 in the power circuit comprising conductors I, 2' closes, thecoil II will be energized and will withdraw the trigger ID from the switch I, allowing said switch to be closed (under the influence of a 35 spring a) on the contact 9 (as shown in Fig. 1). The energizing of the coil l I is but instantaneous since the circuit through the coil is opened immediately that the switch 'I' breaks contact with the trigger Ill. Therefore, the trigger I0 40 immediately resumes its original position (under the influence of a spring) so as to be in the path of contact 30' which impinges on said trigger.

20 leading from the other end of the winding to a trigger armatureZl normally operating to hold the switch 22 out of engagement with a contact 5 r 23, the pivot end of switch 22 being connected to line L by a conductor 24. Thus, the transformer primary winding is connected across the H0 volt line. The secondary winding s of the transformer T is connected to the primary winding 55 by a conductor 25 and at the opposite end to a coil 2'! by a conductor 26, the opposite end of said coil being connected to the spring contacts 9, 9 by a conductor 29. It is thus apparent that the circuit of the transformer secondary is closed when either of the switch levers I, I engage contact 9 or 9. The transformer secondary circuit closed by the action of lever I may be traced as follows:

From one end of the transformer secondary through conductor 26, coil 21, conductor 29, to contact 9, switch lever l, conductor 8', conductor 3', conductor 2, through the closed switch l3 and asymmetric cell E5, to conductor I and line wire L, conductor 18, conductor 19 and transformer secondary. The actuation of the switch lever l breaks the connection between the power circuit and the line and connects the transformer secondary in series with the power circuit I, 2 or I, 2. This results in the flow of a low voltage current from the transformer secondary through the coil 21 and the asymmetric cell l5 causing current to pass through the coil 21 and attract armature 32.

The armature 32 carries a contact element 31 arranged to engage contacts 39 and 40 when coil 21 is energized. In fact, these elements together constitute a simple relay for closing the control circuits which make the alarm circuit and safety circuit operative in case of fire or the safety circuit only in case of a short in one of the power circuits. When the relay (elements 27, 32 and 31) is actuated by the closing of the secondary circuit of transformer T current flows from the line through the alarm control circuit as follows:

From line wire L to conductors l8, l9, and transformer secondary s to the relay through conductors 25 and 4!, thence from contact through conductor 42 to electro-thermal element 43 to conductor 44, contacts 35 and 34, conductor 44' to coil 45, armature 2|, trigger 22, conductor 24 to line wire L. The coil 43 is of sufficiently high resistance so that there will not be enough current flowing through coil 45 to attract armature 2| until the contacts 4'5, 4'! have been brought together. However, in about thirty seconds the contacts 41, 41 will be warped together and the coil 45 energized which causes the release of switch lever 22 to engage contact 23 and close an alarm circuit comprising line wire L, conductor l8, alarm A conductor 24', contact 23, lever 22 and conductor 24 to line wire L. Thus the alarm is sounded to indicate that there is a fire in the part of the building containing the circuits connected to the alarm. At the same time the alarm is sounded the circuit affected is opened by the safety circuit, comprising conductor 3! (connected to the heating coil 46 of element 43), relay switch element 30', armature Ill, coil H, conductor l2 and line wire L. The flow of current through coil H withdraws trigger armature Hi and releases relay switch lever I from the contact 9. Thus the affected circuit is put out of commission.

While the alarm circuit is closed as above described, the alarm cut-out circuit is also closed. This. cut-out circuit in parallel with the transformer secondary circuit comprises line wire L to conductors l8, l9, transformer secondary s to the relay, through conductors 25 and 4|, thence from contact 39 to conductor 38, asymmetric cell 49, conductor 5i, heating element 50, conductor 52, conductor 25, contact 9 or 9, switch lever I or I, conductor 8 or 8, conductor 3 or 3, conductor 2 or 2', thermostat switch I3, asymmetric cell i 5, conductor l or I and line wire L, conductors i 8 and I9 back to the transformer secondary. However, no current flows through the circuit because the asymmetric cell 49 is of opposite polarity to the cell l5 thus blocking the current flow.

In the event of a permanent short circuit in one of the power circuits the control relay (elements 2?, 32, and 37) is actuated in the same manner as before. However, a small current will now flow through the alarm cut-out circuit since the asymmetric cell is no longer in the circuit (having been shorted) and the asymmetric cell 49 blocks out only half of the low potential A. C. wave. The flow of current through heating element 55 causes the thermostatic metal elements 44 and 44" to warp in opposite directions thus separating contacts 34 and 35 before contacts 41, 41 can close. Therefore, the alarm relay circuit (which includes elements 44, 44) will be opened before the alarm relay can be actuated. However, the subsequent closing of contacts 41, 4'] by warping due to the heat of element 43 closes the safety circuit as above described and I" fire in the building, or whether the power circuit 1 has been closed by a short across the line. It will be observed that in the diagram of Fig. 2 the connections of the power circuit and the line are the same as in Fig. 1, and the primary of transformer T is always energized. Therefore, the closing of a switch I3 in the power circuit will cause a low potential (6 volts) current flow through the coil 2'! attracting armature switch 3'! and closing the gaps between said switch and contacts 39 and 49, just as in the main form. 45

However, there will also be a low potential current flow through the alarm control circuit as follows:

From conductor 38, through the parallel circuits made up of conductors 55, 55, asymmetric cells 5?, 58, conductor 58 and heating resistances 69, 6t and conductor 6!, from which point the circuit continues through conductor 29, through the power circuit including the asymmetric cell !5. The polarity of the asymmetric cell I5 is opposed to the polarity of one of the asymmetric cells 51, 53, so current will flow only through one of these cells causing only one of the resistances 60-, E9 to become heated, which results in a warping of one of the heat sensitive conductors 63 or 64 connected between conductor 42 and coil 45. The warping of one of these elements 63 or 64 brings the contacts 65-, 66 together allowing line voltage to flow through this circuit just as it does in the main form (Fig. 1) releasing the switch arm 22 to close the alarm circuit. Obviously, if the switch: 31' is actuated by a short circuit in the power circuit instead of by fire the asymmetric cell 15 in the power circuit is circumvented sothat current will flow through both asymmetric cells 51 and 58, heating both coils 55 and 5! and warping both elements 63 and 64 so that the contacts 65 and 65 remain separated, in which event the alarm circuit is not closed and nogalarm is sounded. Thus, the sounding of the alarm is restricted to such action as takes place under the influence of heat caused by firein the building containing my improved circuits.

The principle of utilizing asymmetric cells to control the closing of the alarm circuit may also be applied, as shown in Fig. 3, wherein I substi tute a parallel circuit containing asymmetric cells, similar to that of Fig. 2 for the respective power circuit relays shown in Fig. 1. In the diagram shown in Fig. 3 the closing of the heat actuated switch I3 destroys the fuse 6, thereby causing line current to flow through conductor 8 to heating coils ill and H. Heating coil H1 is in series with asymmetric cell 72 and heating coil H is in series with asymmetric cell 13 constituting paral lel circuits, both of which are in series with the power circuit (after the destruction of fuse 6) through the conductor M. Therefore, when theswitch 13 is closed current will flow through only one of the asymmetric cells l2, l3 and its associated resistance Ill or f 5 because the cells 12 and '33 are of opposite polarity. Therefore, one of the heat responsive elements l5, it will be warped so as to close the gap between the terminal con-- tacts of these elements which closes the alarm circuit as follows:

From line wire L to switch lever 22, through trigger armature 2|, coil 55, conductor 45, element 16, element 15, conductor ll, conductor M and line wire L. The actuatoin of the alarm relay (2|, 22, and 45) causes switch lever 22 to engage contact 23 connecting the alarm circuit (not shown) directly to line wire L. Obviously, the alarm circuit would be closed even though the alarm relay were dispensed with, but it would only be closed so long as elements l5, l6 were in engagement and the engagement of these elements is dependent on the operativeness of the power circuit. Therefore, the relay is interposed so as to make certain that the alarm circuit would remain closed after having once been closed even though the power circuit should subsequently become inoperative.

We claim:

1. A combined power and alarm system comprising a power circuit connected to a source of power and including a fuse in series therewith, a two-step electromagnetically operated device having a stepping magnet for controlling the stepping thereof normally connected in shunt to said fuse, a normally open alarm switch and an asymmetric cell, a connection across the power circuit including in series the alarm switch and the asymmetric cell, the capacity of the fuse being such that upon the occurrence of a short across the power circuit or upon the closure of the alarm switch the fuse will blow, thereby diverting current to the stepping magnet and cause the stepping magnet to step the two-step device one step,

switching means operated by the first step of the device for opening the first magnet circuit by disconnecting the power source from the power circuit and preparing a second circuit therefor, an alarm circuit, means for differentiating be- 5 tween the closure of the alarm switch and a short across the power circuit, said means comprising, an alarm actuating switch included in the alarm circuit and an operating circuit therefor, an alarm cut out switch associated with the alarm circuit 10 to prevent its completion and an operating circuit therefor including in series an asymmetric cell of opposite polarity to the first cell, means also operated on the first step of the device for associating the power circuit with the differentiating means, means operated by the closure of the alarm switch or the occurrence of a short for closing the alarm actuating switch operating circuit after a predetermined interval and for completing the second stepping circuit, said operating circuit for the alarm cutout switch, due to the oppositely poled cell, being effective to prevent the completion of the alarm circuit in case of a short and ineffective in case of the closure of the alarm switch and means controlled by the second step of the device for disassociating the differentiating means from the power circuit to thereby prevent further response of the differentiating means to the power circuit.

2. A composite power and alarm system comprising a power circuit connected to an alternating current source of power and including a fuse in series therewith, a connection across the power circuit including in series a normally open alarm switch, and an asymmetric cell, the capacity of the fuse being such that upon the occurrence of a short across the power circuit or upon the closure of the alarm switch the fuse will blow,

differentiating means for differentiating between a short on the power line and the closure of the alarm switch comprising two parallel connections each including in series an asymmetric cell and a heating resistance, the cells being oppositely arranged in said parallel connections, circuit arrangements whereby the parallel connections will be effectively placed in series with the power line upon the blowing of the fuse to thereby energize both of the heating elements in case of a short and one only of the heating elements in case the alarm switch is closed, two opposed bimetallic elements each having one of the-heating elements associated therewith, whereby when one only of the heating elements is energized one of the bimetallic elements will be moved to engage the other and if both are energized no engagement will occur and alarm means operated by such engagement.

ROGER W. MCBRIEN. NORVAL F. WILSON. 

